Topic
Bipolaron
About: Bipolaron is a research topic. Over the lifetime, 1335 publications have been published within this topic receiving 29154 citations. The topic is also known as: bipolarons.
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01 Jan 1992
TL;DR: In this article, the authors derived the selfconsistent Bloch eigenfunctions and the ground state energy of the soliton and bipolaron lattice solutions for these models to investigate the thermodynamic stability and to calculate the wave number dependent electronic dielectric function e(q,ω) in random phase approximation.
Abstract: The continuum version [1] of the Su-Schrieffer-Heeger model [2] may be generalized to include an external bond [3] and/or site dimerization [5] in order to describe the physical properties of non-degenerate ground state and/or diatomic polymers. We have derived the selfconsistent Bloch eigenfunctions and the ground state energy of the soliton and bipolaron lattice solutions for these models to investigate the thermodynamic stability and to calculate the wave number dependent electronic dielectric function e(q,ω) in random phase approximation. After Kramers-Kronig transformation the loss function and the plasmon dispersion were determined and compared with results of electron energy loss experiments [4].
TL;DR: The ground state energies of polaron Ep and bipolaron EB in three-dimensional lightly doped cuprates are calculated variationally taking into account the short and long-range electron-phonon interactions and Coulomb correlation in the continuum model and adiabatic approximation as mentioned in this paper.
Abstract: The ground-state energies of large polaron Ep and bipolaron EB in three-dimensional lightly doped cuprates are calculated variationally taking into account the short- and long-range electron-phonon interactions and Coulomb correlation in the continuum model and adiabatic approximation. The binding energy of a large bipolaron and its stability region are determined as a function of the ratio of dielectric constants η = e∞/e0. It is found that the large bipolaron is stable in a broad region of η.
TL;DR: In this article, the theoretical electronic structure of poly(trans-1,4-di(2-thienyl)-1,3-butadiene) (PTB) was investigated and the optical properties of its neutral and doped oligomers were determined.
Abstract: In the present work we investigated the theoretical electronic structure of poly(trans-1,4-di(2-thienyl)-1,3-butadiene) (PTB) and determined the optical properties of its neutral and doped oligomers. Geometrical optimizations were at the semiempirical level by using the Austin method 1 (AM1). The band structure of π electrons regarding to the neutral PTB polymer was obtained by using a tight-binding Hamiltonian. The densities of electronic states (DOS) for neutral and doped copolymers were calculated by using the negative factor counting technique. The spatial charge distribution of the oligomeric chain was also analyzed. The energy of the electronic transitions and their associated oscillator strength values were calculated for the neutral, double, and single charged oligomers to determine the UV–vis absorption spectra. The calculations were performed using the intermediate neglect of differential overlap Hamiltonian in combination with the single configuration-interaction technique in order to include correlation effects. The band gap obtained in the PTB was about 2.101 eV for the optics absorption and 1.73 eV for the DOS. The bipolaron states appear in the gap, about 0.57 eV and 0.48 eV below and above the conduction and valence bands, respectively. When the dopants concentration is increased the DOS showed that the energy gap tends to vanish, which may lead to semiconductor–metal transition. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
24 Mar 2023
TL;DR: In this paper , the formation of polarons and bipolarons in n-doped poly(benzodifurandione) polyacetylene (PBDF) was investigated by taking long oligomers and 1D periodic chains as model systems.
Abstract: The seminal development of highly electrically conducting polyacetylene via oxidative or reductive treatment (“doping”) has continuously inspired the search for other conducting π-conjugated polymers. Recently, poly(benzodifurandione), PBDF, was reported to have unexpected solubility given the absence of side chains and to exhibit an unprecedented, high electrical conductivity upon reduction (“n-doping”), with protons acting as counter-ions. Here, we theoretically investigate the electronic and magnetic properties of PBDF by taking long oligomers and one-dimensional (1D) periodic chains as model systems. With the oligomer models, we characterize the formation of polarons and bipolarons in n-doped PBDF. Our results indicate that singlet bipolarons tend to be the energetically most favorable species when protons bind to two adjacent carbonyl groups in nearest-neighbor benzodifuran moieties. The calculations on the 1D periodic chain models show that the positions of the protonated carbonyl groups determine the metallic, semiconducting, or insulating nature of a PBDF chain. When the protonated carbonyl groups are all situated on the same side of a PBDF chain, a stable helical chain configuration is found that exhibits ferromagnetic behavior. Our findings elucidate the mechanism of polaron and bipolaron formation in long oligomers of n-doped PBDF and highlight the fascinating electronic and magnetic properties of periodic 1D chains. These studies also provide a steppingstone for the investigations of PBDF thin films, for which two- and three-dimensional structures must be considered.
27 Jun 2023
TL;DR: In this paper , the formation of spin-orbital bipolarons in the electron-doped SO-coupled Mott insulator has been studied and it has been shown that these two seemingly mutually exclusive interactions are entangled.
Abstract: Polarons and spin-orbit (SO) coupling are distinct quantum effects that play a critical role in charge transport and spin-orbitronics. Polarons originate from strong electron-phonon interaction and are ubiquitous in polarizable materials featuring electron localization, in particular $\mathrm{3d}$ transition metal oxides (TMOs). On the other hand, the relativistic coupling between the spin and orbital angular momentum is notable in lattices with heavy atoms and develops in $\mathrm{5d}$ TMOs, where electrons are spatially delocalized. Here we combine ab initio calculations and magnetic measurements to show that these two seemingly mutually exclusive interactions are entangled in the electron-doped SO-coupled Mott insulator $\mathrm{Ba_2Na_{1-x}Ca_xOsO_6}$ ($0< x < 1$), unveiling the formation of spin-orbital bipolarons. Polaron charge trapping, favoured by the Jahn-Teller lattice activity, converts the Os $\mathrm{5d^1}$ spin-orbital $\mathrm{J_{eff}=3/2}$ levels, characteristic of the parent compound $\mathrm{Ba_2NaOsO_6}$ (BNOO), into a bipolaron $\mathrm{5d^2}$ $\mathrm{J_{eff}=2}$ manifold, leading to the coexistence of different J-effective states in a single-phase material. The gradual increase of bipolarons with increasing doping creates robust in-gap states that prevents the transition to a metal phase even at ultrahigh doping, thus preserving the Mott gap across the entire doping range from $\mathrm{d^1}$ BNOO to $\mathrm{d^2}$ $\mathrm{Ba_2CaOsO_6}$ (BCOO).